For roofing assemblies, building codes require the installation of an underlayment on a roof deck before installing the final roof covering, such as shingles. Such underlayments are typically strips of material that are attached to the roof deck and overlapped to create a downward drainage plane. The underlayment provides a secondary moisture barrier for the roof deck, in addition to the outer roof covering.
One of the functions of a roof system is to insulate a building and, thereby, conserve energy for the heating or cooling energy of a building. It is, therefore, desirable to provide additional thermal insulation to a roof deck of a roof system to both prevent heat from escaping from the building and protect the building from external heat gain for energy efficiency purposes. Thermal insulation is measured by R-value, which is the thermal resistance to heat flow. The U-factor is the inverse, or reciprocal, of the total R-value, i.e.: U-factor=1/Total R-value. A larger R-value means that the material or system has greater thermal resistance and more insulating ability as compared to a smaller R-value. Such R-values can be added together. For instance, for homogeneous assemblies, the total R-value of an insulation assembly is the sum of the R-value of each layer of the assembly. These layers may include sheathing and finishes, the insulation itself, air films, and weatherproofing elements.
Recently, there have been new energy efficiency standards on roofing assemblies to encourage energy efficiency in buildings. One solution to meet the new standards is the use of a reflective insulation material that incorporates a low emittance surface on one or both sides. These materials reflect up to 97% of radiant energy or re-emit up to 3% from the building interior's heat loss or heat gain from the outside. Such reflective insulation may be applied in addition to an approved underlayment to achieve the desired additional thermal insulation for roof systems. One example of a conventional reflective insulation product is Low-E Insulation manufactured by Environmentally Safe Products of New Oxford, Pa.
Like other reflective insulation products, the Low-E product is an effective thermal insulation addition to a metal, tile, or composite shingle roof covering. The application of such products offer the first R-value or values to address the heat before it would enter the attic space. By doing so, reflective insulations such as Low-E Insulation greatly reduce the heat transfer across a roofing system, which allows for lower BTU gain or loss, which in turn equates to energy savings for the consumer.
Such a reflective layer product has been used in roof applications for some time, but requires the additional cost and labor associated into combining it with an approved roof underlayment product. With reflective products in combination with an approved underlayment, the thermal performance aspect is well-received. However, a reflective product must be installed with an International Code Council (ICC)-approved roofing underlayment. This dual-product approach equates to extra material cost in addition to more than twice the labor cost, since the extra reflective product must be installed in addition to the conventional underlayment. Due to the conventional reflective insulation products not having ICC approval as a standalone underlayment, these costs are required for the redundant application of the thermal sheet to approved underlayment to be considered compliant with ICC and other building code standards. This extra cost significantly extends the cost-cycle payback for the consumer and, hence, limits the full value to the construction market and its consumers.
Currently, underlayment products must comply with ASTM D 226, Type I or ASTM D 4869 Type I standards under ICC Acceptance Criteria 188 (ICC AC 188). The specific Acceptance Criteria required to meet this code is detailed in http://www.icc-es.org/Criteria_Development/1202-post/9_AC188_final.pdf. Reflective products such as Low-E Insulation do not meet the criteria of ICC AC 188.
This cost-to-benefit ratio leaves many users unable to enjoy the benefits of an energy upgrade to a roof due to the additional upfront investment in the reflective layer product combined with approved underlayment. To be considered an energy-efficiency upgrade, the reflective layer product must meet strict criteria for aging and weathering of samples before testing physical properties in accordance with AC 188. Reflective products of traditional designs do not meet these standards and require reformatting of the design to meet benchmarks. Thus, even if the additional upgrades are implemented, the lack of a reflective product that meets standards is an impediment to upgrading existing roofs and installed underlayments.
An insulation or insulation system is measured for thermal performance. However, it is also measured for cost-cycle payback. The former is well known, as all products are marketed on their R- or U-value contribution to the system. However the latter is as important a factor, if not more important than thermal performance. The laws of diminishing returns demonstrate this point. Consider constructing a system that is twice as good as a thermal code requirement with regard to R-value, but requires four times the cost as a code compliant system. Although one is far superior with regard to thermal performance, as stated by R-value, the diminishing returns demonstrate a far less than two times the effect to energy performance. To achieve this two times R standard, a larger capital investment must be made. When applying the laws of diminishing returns to increased R-value and the additional investment, the time it takes for investment to produce a return is far too long and, although the superior system produces additional savings when compared to the standard, the effect is nominal. The performance/investment return for an energy upgrade is the cost-cycle payback. Although energy upgrades should be performed for existing or new structures for energy-conservation purposes, applying this balanced approach of the cost-cycle payback allows consumers to make a more-informed decision when investing in the energy performance of their homes. For this reason, all insulation products and/or systems are weighed for this measurement, as well as for specific thermal performance.
Attempts to provide an underlayment product with appropriate insulation have failed. The addition of insulation requires strength in both machine- and cross-direction, creating the need for reinforcement in the form of a reinforcement layer or layers. However, aging and weathering cause such products to fail because the reinforcement layer promotes wicking of moisture and causes delamination of the product when using traditional design practices.
Accordingly, a need exists for providing an underlayment that meets the building code's AC 188 Standard but also provides a thermal insulation. There is also a need for an underlayment that provides thermal insulation but may be installed as a conventional underlayment. There is also a need for an underlayment with appropriate reinforcement materials that does not interfere with moisture resistance.